Adsorption Kinetics-Driven Humidity-Resistant C2H2/CO2 Separation by a Hydrophilic Metal–Organic Framework

The separation of C2H2/CO2 under highly humid conditions by using metal–organic frameworks (MOFs) is extremely challenging because water vapor would reduce the C2H2 adsorption capacity or even degrade the structure of MOFs. In this work, a zirconium zeolitic metal–organic framework (NNM-5) with a small aperture and large cavities exhibits commendable C2H2/CO2 selectivity (16.6 at 298 K and 1 bar) and a high uptake ratio (3.13 at 298 K and 1 bar). More importantly, NNM-5 could maintain at least five breakthrough cycles under highly humid conditions (around 100% RH) without performance degradation compared to that under dry conditions. Our studies indicate that the kinetic mechanism is the key to excellent separation performance under highly humid conditions based on the fact that the material is hydrophilic with a high water uptake, but the diffusion rate of H2O is 2 orders slower than that of C2H2 and CO2 in NNM-5.